Combined air-hydraulic actuating system



Jan. 2, 1945. w. F. BOLDT 2,366,310

' NED AIR-HYD AULIC Fild Jan. 7. 1943 s s hhhh s-Sheet 1 1| www ,4

INVE NTOR ATTOV RRRR Jan. 2,1945. w, D-r 2,366,310

COMBINED AIR-HYDRAULIC ACTUATING SYSTEM Filed Jan. '7, 1943 5 Sheets-Sheet 2 L "I v.

% IN ENTOR v 5 I W.F.BQLDT 7 ATTORNEY' Jane 2 w. F COMBINED AIR-HYDRAULIC ACTUATING SYSTEM Filed-Jan. 7. 1943 3 Sheets-Sheet 3 INVENTORY W. BOLDT A-TTORNEY Patented Jan. 2,1945

COMBINED AIR-HYDRAULIC ACTUATING SYSTEM Werner F. Boldt, Clayton, Mo., assignor to Wagner Electric Corporation, St. Louis, Mo., a corporation of Delaware Application January 7, 1943, Serial No. 471,552

19 Claims.

My invention relates to actuating systems and.

moreparticularly to one in which both air and liquid under pressure is employed.

One of the objects of my invention is to produce an air-hydraulic actuating system includin an improved combined hydraulic selector valve and air control valve mechanism which will permit the simultaneous actuation of a plurality of devices or the selective actuation of certain of said devices only.

Another object of my invention is to produce an improved selector and control valve mechanism for use in a combined air-hydraulic actuating system which will ermit said system to'be controlled in a desired manner by a single-control member.

Still another object of my invention is to pro- I duce an improved actuating system in which air pressure is employed to develop hydraulic pressure for operating a plurality of devices and to embody in said system a valve mechanism permitting control of the air pressure and/or selective operation of the devices by a single manually operable member.

A more specific object of my invention is to produce an improved combined air-hydraulic actuating system for the brakes of a vehicle or vehicles which will permit the operator to so control the brakes thereof that they can be an aid to steering.

Other objects of my invention will become apparent from the following description taken in connection with the accompanying drawings in whichFigure 1 is a schematic view of a brakin system for a vehicle in which my invention is embodied; Figure 2 is a front view of my improved control valve mechanism; Figure 3 is a longitudinal sectional view of the combination valve mechanism; Figures 4 and 5 are sectional views taken on the lines 4-4 and 5-5, respectively, of Figure 3; and Figure 6 is a schematic view showing how the braking system can also be employed on a-tractor-trailer vehicle.

Referring to the drawings in detail and first to Figure 1, there is shown a braking system for a vehicle having dirlgiblewheels I and 2 for steering, right hand driving wheels 8, and left hand driving wheels 4. Each of the wheels is shown as being provided with a braking assembly 5 actuated'by a hydraulic fluid motor 5'. The source of hydraulic pressure is a master cylinder device 8 of known construction. The outlet of this master cylinder is connected to aconduit l which vleads to my improved combination control valve mechanism 8 shown in detail in Figures 2, 3, 4,

and 5 to be later described in detail. Leading from this valve mechanism is a conduit 9 connected tothe fluid motors of the dirigiblewheel brakes. Conduits l0 and also lead from the valve mechanism, the former being connected to the fluid motor of the brakes on the'right driving wheels 3 and the latter to the fluid motors of the brakes on the left driving wheels 4.

I The master cylinder device is adapted to be operated by a power cylinder i2 which is operated by air under pressure from a suitable source such as reservoir l3. Communication between the air reservoir and the power cylinder is permitted through either a part of the control valve mechanism 8 or through a foot-controlled valve l4. Conduit 15 leads from the reservoir to the valve mechanism 8 and another conduit 16 lead from the'reservoir to the toot-controlled valve which may be of any desired construction but preferably of the metering type. The power cylinder I2 is connected to the valve mechanism 8 and the footcontrolled valve by means of a common conduit l1, branch conduits l8 and I9. and a two-way valve 20. This two-way valve comprises a cylinder 2| and a floating piston valve 22. When the foot-controlled valve is opened to admit air to the branch conduit I8, the piston of the two-way valve will close off conduit l9 and connect conduit l8 to conduit l1 and the power cylinder and when air is admitted to conduit l9 through valve mechanism 8, piston 22 will close 011 conduit l8 and connect conduit l9 to conduit l1 and the power cylinder.

Referring now to Figures 2, 3, 4, and 5, the details of the combination control valve mechanism 8 will be described. This mechanism has a main body member 23, a bottom plate 24, and a top casing member 25. The body member and bottom plate member are so formed as to provide a chamber 26 therebetween to which is connected conduit 1 coming from the outlet of the master cylinder device 6. This chamber 26 has three outlet passages 21, 28, and 29 (see Figure 5) arranged 180 degrees apart inthe body member 23. The outlet passage 21 is connected with conduit 9 leading to the front brakes and passages 28 and 28 are connected to conduits II and I0,

34 biases each plunger toward seated or closed position. The valves are controlled by a disc cam 35 mounted in the body member 23 with its peripheral portion being received in cross-notches 36 in the valve plunger so that the cam surfaces, which are formed as flanges on the disc, may cause the plu'ngers to be reciprocated. As best shown in Figures 3 .and .5, the disc cam has a short high portion 31 cooperating with the plunger of valve 30 and'a long high portion 38 extending over approximately 120 degrees for cooperation with the plungers of valves 3| and 32.

Between the high portions 31 and 38 are low portions 39 and 40.

When the disc is in its normally inoperative position, as shown in the figures, the high portions thereof will be so positioned that all the plungers of the valves will be held in unseated position. If the disc should be turned in a clockwise direction, as viewed in Figure 5, the plungers of valves 30 and 3| will be moved to valve closed position by the action of springs 34 due to the fact that the low portions 39 and 40 of the cam are moved into the slots of the plungers. If the disc should be moved in a counter-clockwise direction, then the plungers of valves 30 and 32 will'be moved to closed positions by the springs due to the fact that the low portions 39 and 40 are moved into the slots of said plungers.

The disc is provided with a stem 4| which exends through the body member 23 and into the casing member 25 and in order to seal the stem, a sealing washer. 42 is provided which iscompressed by a spring 43 acting on the disc and positioned between said disc and the bottom plate. The inner end of the stem has a rectangular cross-section and is received in a rectangular opening in a member 44. This member is journaled in the body member 23 and in the inner end of a cylinder 45 in casing 25 for both rotative and axial movement. The end of member 44 adjacent the body member 23 is formed with a cam surface 46 for cooperation with a complementary cam surface 41 carried by the body member (see Figure 3). The member 44 is adapted to be turned by a lever or handle 48 which is pivoted to said member by pins 49 (Figure said handle projecting through a curved slot 50 in the wall of the casing member in order to be accessible from the exterior. A spring 5| mounted in the casing member 25 is adapted to act on member 44 to hold the cooperatingcam surfaces 46 and 41 in engagement with each other. Said spring. also acts on the handle to bias it into engagement with the lower edge of the slot and hold it in proper extended position.

When the handle is in the central part of the slot, cam surfaces 46 and 41 on member 44 and body member I3 will be in complementar engagement and disc 35 will have the position shown in Figure 5 wherein all the shut-off valves are in open position. If the handle should be moved to the right, as viewed .in Figure 2, member 44 will be rotated and also disc 35. This will position the disc so that valves 36 and 3| become closed, valve 32 remaining open. The cam surfaces 46 and 41 will cause member 44 to move upwardly and compress spring 5|. If, after moving the handle to the right, the operator should release said handle, spring 5| acting through cam surfaces 46 and 41 will return the handle to its central position. The disc also returns to the I position wherein all the shut-01f valves will again be held open. If the lever should be turned to the left, as viewed in Figure 2, the will be hicle to, the left.

so rotated that the shut-off valves and 32 will be permitted to become closed, shut-off valve 3| remaining open. Spring 5| will again be compressed by member 44 being moved upwardly by the action of cam surfaces 46 and 41. When the operators hand is released from the handle, the handle will snap back to its central position under the action of spring 5|.

The bleecler valve 52 is associated with chamber 26 so that air can be removed from the hydraulic system when filling it with liquid or at any other time.

From the foregoing description it is apparent that when it is desired toemploy the brakes to assist in steering, such can be accomplished solely by controlling the shut-off valves. By turning handle 48 to the left, as viewed from the front of the valve mechanism 8, the master cylinder device 6 will be cut off from the fluid motors of the brakes on the dirigible wheels and also from the fluid motors of the right driving wheel brakes. When the master cylinder is now operated, only the brakes on the left driving wheels will be applied. Thus the operator of the vehicle will be aided by this braking in turning the ve- Steering will be greatly facilitated, particularly in the event the vehicle is on icy or very slippery ground where the dirigible wheels, although turned, will not cause efiicient turning of the vehicle. that when a rear wheel is braked to aid in steering, the front wheels are always free to turn. If it should be desired to employ the brakes in steering to the right, the handle may only be moved to the right end of the slot. This will cause the brakes on the dirigible wheels and the left driving wheel brakes to be cut off from the master cylinder device and when said device is operated, only the brakes on the right driving wheels will be applied.

No manual effort need be employed to bring the handle back to its normally inoperative position as this will be. automatically accomplished by spring 5| whenever the hand is removed from the handle. If the handle is in its central position, all the shut-ofi valves will be open and thus they will not in any way interfere with the ap-, plication of all the brakes on, both the front and rear wheels of the vehicle.

Handle 48 is also employed to control the operation of the master cylinder device by air pressure and in order to accomplish this, there is an air metering valve embodied in the control valve mechanism 8. As shown in Figure 3, this metering valve .is associated with the previously mentioned cylinder 45 of the casing member 25. The outer end of cylinder 45 is provided with a closure member 53 to which is connected conduit I5 coming from reservoir l3. Within chamber 54 of said member is an inlet valve element 55 for controlling communication between said chamber and the adjacent end of the cylinder by way of an opening 56. The valve 55 is normally held seated by a spring 51. Within cylinder 45 is a piston'58 having an exhaust passage 59 which communicates with an. opening 66 in the cylinder leading to the atmosphere. The exhaust passage 59 is controlled by an exhaust valve element tween piston 58' and the previously referred to rotatable and axially movable member 44 which It is also to be noted has one end journaled in the'cylinden there is positioned a relatively strong spring 65 which is normally in an uncompressed condition when the exhaust valve element is open. The piston is held in engagement with this spring by a light spring 66 positioned between the forward end of the piston and member 53. The piston, when held against spring 65, causes exhaust valve element 62 to be opened so that the portion of the cylinder ahead of the piston is in communication with atmosphere.

When handle 48.is in the central position of the slot, the parts of the metering valve of the valve mechanism 8will be in the positions shown in Figure 8. The inlet valve element 55 will be closed and the exhaust valve element 62 will be opened. Thus no air under pressure from the reservoir can enter the cylinder and conduit l9 leading to the power cylinder l2 for actuating the master cylinder device. When handle 48 is turned either to the left or to the right, member 44 will be moved axially upwardly as already mentioned, such movement being brought about by cam surfaces 46 and 47. This will result in piston 58 being moved through spring 65 so that the exhaust valve element 62 will be closed and then the inlet valve element 55 opened, The opening of valve element 55 will occur after disc 35 has permitted the controlled shut-01f valves to become closed, said closing occurring when the handle has been moved only a portion of the distance toward either end of slot 55. When the inlet valve element 55 is opened, air under pressure will be admitted through passage 56 to conduit It. This will operate the two-way valve 20 so that conduit I9 will be connected to conduit It only, thereby causing operation of the power cylinder I 2 and actuation of the master cylinder device 5. When the master cylinder device is actuated, hydraulic pressure will be developed and either the right or the left driving wheel brakes only applied depending upon the direct on of movement of the handle and the shut-off remaining open.

The extent of movement of the handle toward either end of the slot will control the amount of air under pressure admitted to the power cylinder and consequently the amount of hydraulic pressure developedu This result is obtained by the extent of compression of spring 55. When the inlet valve 55 is initially opened, air pressure will be built up ahead of piston 58 and will compress spring 65. As this spring is compressed,

piston 58 will be so moved as to permit the inlet valve to again close. If spring 65 is further compressed, the valve element 55 will again be opened and additional air under pressure will be admitted until spring 65 is so compressed that inlet valve 55 will again become closed. Thus the air control valve acts in the well-known metering manner.

From the foregoing description of the entire system it is seen that operation of handle 48 in either direction from a central position will cause the master cylinder device to be operated and a brake on a driving wheel applied. The brake which isapplied will dependu-pon the direction in which handle 48 is moved. To release. the brakes all that is necessary-is to remove the hand from the handle and permit spring 5| to return said handle to neutral position. When the handle assumes its neutral position the air which has been admitted to the power cylinder will be exhausted to atmosphere by the opening of the exhaust valve element 52.

Handle 48 is also so arranged that it can operate the metering valve without controlling the shut-oil valves. This is accomplished by pushing downwardly on the outer end of the handle when it is in its central position. Under such conditions it will fulcrum on the lower edge of the slot and lift member 44 upwardly to thus compress spring 65 and operate the metering valve in the same manner as was done when member 44 was moved upwardly by cams 48 and El. As shown in Figures 2 and 3, the edge of the slot at its center is rounded as indicated by numeral 61 in order-that the handle can be easily rocked. The lever adjacent member 44 is also cut away at 68 and 69 to permit free pivotal movement of the handle.- Although all the brakes can be applied by rocking handle 48, such is generally only operated when it is inconvenient to use the footcontrolled valve I4, By operating the foot-con:

trolled valve, air under pressure from the reser voir will flow by way of conduits it and it to conduit I! in the power cylinder to thus actuate the master cylinder device and cause hydraulic pressure to be developed to operate all the brakes, the shut-oif valves remaining in open condition. When the foot-controlled valve is operated, the two-way valve will function to permit communication between conduits i8 and i7 and prevent any communication with conduit is.

From the foregoing it is seen that in the system described there is provided a combined airhydrauli c brake actuating system whereby all the brakes may be applied by operation of a footcontrolled valve or all the brakes may be operated by moving a handle to operate another control valve. In addition to this, the handle may be so operated that only the brake of a driving wheel or wheels on one side of the vehicle may be complished by merely plugging passage 2'5 to which conduit 9 is connected. Conduit it? will be connected to all the brakes on the right side of the vehicle and conduit M will be connected to all the brakes on the left side of the vehicle.

In Figure 6 there is schematically disclosed a braking system similar to that shown in Figure 1 but adapted also for controlling the brakes on a trailer vehicle which may be connected to the main or tractor vehicle such as that of Figure 1. In this figure the parts which are the same as those employed in the system of Figure 1 are indicated by the same reference characters.

,This is the entire braking system for the tractor vehicle which is shown as being provided with driving right and left tracks 3 and 4' instead of driving wheels. The driving members for these tracks are provided with brakes 5.

The trailer vehicle is also shown. as one having tracks 10 although a wheeled one could be employed. The brakes H for these tracks'are actuated by power cylinders" and are connected 'by conduits 13 and a relay valve 14 of any suittor, the connection comprising a conduit 80 (connected to conduit l8 leading from the foot-controlled valve) a coupling 8| and a conduit 82 connected to the relay valve.

The trailer brakes will not be affected in any way by the control of the tractor brakes when the combination control valve mechanism 8 is operated by handle 48 in a manner already described in connection with the system of Figure 1. When the foot-controlled valve 14, however, is operated, all the brakes on both the tractor and trailer will be applied since the air admitted by the foot-controlled valve will so operate the relay valve I4 that the air pressure in the trailer reservoir will be admitted to the power cylinders 12. With this braking system on a tractor-trailer combination vehicle, the operator may control all the brakes on both vehicles, all the brakes on the tractor vehicle only or selectively the brakes on the driving members of the tractor vehicle only in order to assist in steering.

Being aware of the possibility of modifications in the particular structure herein described without departing from the fundamental principles of my invention, I do not, intend that its scope be limited except as set forth by the appended claims.

Having fully described my invention, what I claim as new and desire to secure by Letters Patent of the United States is:

1. In an actuating system, two fluid pressure operated actuating motors, a hydraulic pressure developing device, conduit means for placing said device in communication with each motor, two shut-oil. valves each of which is capable of preventing developed hydraulic pressure from operating a motor, means comprising a single movable member for selectively closing said valves, a source of air pressure, a power cylinder for actuating the hydraulic pressure developing device, conduit means between the source of air pressure and the power cylinder, a control valve for said last named conduit means, and other means operated by said single movable member for opening the control valve after it has closed said shut-off valves.

- 2. In an actuating system, three fluid pressure operated actuating motors, a hydraulic pressure developing device, conduit means for placing said device in communication with each motor, three shut-01f valves each of which is' capable or preventing developed hydraulic pressure from oper-.

ating a motor, means comprising a single movable member for closing one of the three shut-of! valves together with either or the remaining two shut-off valves, a source-of air pressure, a power cylinder for actuating the hydraulic pressure developing device, conduit means between the source and the power cylinder, a control valve for said last named conduit means, and means for opening the control valve by said single movablemember afterit has closed two shut-oil valves.

3. ,In an actuating system, two fluid pressure operated actuating motors, a hydraulic pressure developing device, conduit means for placing said device in communication with each motor, two

shut-off valves each of which is capable of preventing developed hydraulicpressure from oper- .ating a motor, means for selectively closing said valves, a source of air Pressure, a power cylinder for actuatingthe pressure'developing device, conduit means between said source or air pressure and power cylinder, 'a control valve for said last valve.

4. In an actuating system, two fluid pressure operated actuating motors, a hydraulic pressure developing device, conduit means for placing said device in communication with each motor, two

shut-ofl valves each of which is capable of preventing developed hydraulic pressure from operating a motor, means for selectively closing said valves, a source of air pressure, a power cylinder for actuating the pressure developing device, conduit means between the source and power cylinder, a control valve for said last named conduit means, means for opening the control valve, a singlemember for operating the means for closing the shut-off valves and the means for opening the control valve, and means comprising a second control valve for placing the source of air pressure in communication with the power cylinder independently of the operation of the first control valve by the single member.

, 5. In an actuating system, two fluid pressure operated actuating motors; a hydraulic pressure developing device, conduit means for placing said device in communication with each motor, two

shut-off valves each of which is capable of premeans, means for opening the control valve, and

a single member for operating the means for selectively closing the shut-oil valves and the means for opening the control valve, said member being movable in one direction from a predetermined-position for first closing one shut-oil valve and then opening the control valve and movable in another direction for first closing the other shut-off valve and then opening the control valve.

6. In an actuating system, three fluid pressure actuating motors, a hydraulic pressure developing device, conduit means for placing said device in communication with each .motor, three shut-on valves associated with the conduit means each of which is capable of cutting all communication between the hydraulic pressure developing device and motor, means comprising a member for con rolling said valves and having a position wh; re all the valves are open and other positions where one valve together with either one of the other two valves are selectively closed, a source of air pressure, a power 'cylinder for actuating the hydraulic pressure developing device, conduit means'between the source and power cylinder, a control valve for said last named conduit means, means for opening the control valve, and a single member for operating the means for closing the shut-oil valves and also op erating the'means for opening the control valv (said control valve being opened after the mean, for controlling the shutoff valves has been moved to} either of its said other positions to cause closing of two of the shut-off valves.

7. In an actuating system, three fluid pressure actuating motors, a'hydraulic pressure developing device, conduit means for placing said device in communication with each motor, three shutoff valves associated with the conduit means each of which is capable of cutting off communication between the hydraulic pressure developing device and a motor, means comprising a member for controlling ,said valves and having a position where all the valves are open and other positions .where one valve together with either one of the other two valves are selectively closed, a source of air pressure, a power cylinder for actuating the hydraulic pressure developing device, conduit means between the source and power cylinder, a control valve for said last named conduit means, means for opening the control valve, a single member for operating the means for closing the shut-off valves and also operating the means for opening the control valve, said control valve being opened after the means for controlling the shutoff valves has been moved to either of its said other positions to cause closing of two of the shut-off valves, and other means comprising a second control valve for placing the power cylinmeans for actuating all the brakes, two shut-off der in communication with the source of air pressure independently of the first named control valve.

8. In an actuating system, two fluid pressure operated actuating motors, a hydraulic pressure developing device, conduit means for placing said device in communication with each motor, two shut-ofi ,valves each of which is capable of preventing developed hydraulic pressure from operating a motor, means for selectively closing said valves, a source of air pressure, a power cylinder for actuating the pressure developing device, conduit means between the source and power cylinder, a control valve for said last named conduit means, means for opening the control valve, a singl member for operating the means for closing the shut-off valves and the means for opening the control valve, said member being movable in one direction from a predetermined position for first closing one shut-off valve and then opening the control valve and movable in another direction for first closing the other shut-ofi valve and then opening the control valve, and means for opening the control valve independently of the closing of the shut-oil valves and by movement of the single member in a third direction.

9. In a brake, actuating system for a vehicle having a driving member for each side thereof, brakes for the members, a hydraulic actuating means for actuating all the brakes, shut-off valves each of which is capable of preventing a brake from being actuated, an air pressure system comprising a control valve for operating the hydraulic actuating means, and a single member for selectively closing the shut-oil. valves and opening the control valve after either shut-oil? valve is closed.

10.. In a brake-actuating system for a vehicle having a driving member for each side thereof, brakes for the members, a hydraulic actuating means for actuating all the brakes, shut-off valves each of which is capable of preventing a brake from being actuated, an air pressure system comprising a control valve for operating the hydraulic actuating means, and a single member for selectively closing the shut-off Valves and for opening the control valve after either shut-01f valve is closed or for opening the control valve without'closing a shut-off valve.

11. Ina brake actuating; system for a vehicle having a driving member for each side thereof,- brakes for the members, a hydraulic actuating ,'means for actuating all the brakes, two shut-off valves each capable of preventing a brake from being actuated, a rotatable cam for controlling the selective closing of the .valves, an air pressure system including a control valve for operating the hydraulic actuating means, a reciprocable member for operating the control member, and

means comprising a lever for rotating said cam and so reciprocating the member that either shutoff valve can be closed and the control valve subsequently opened;

13. In a brake actuating system for a vehicle having a driving member for each side thereof, brakes for the members, a hydraulic actuating means for actuating all the brakes, two shut-off valves each capable of preventing a brake from being actuated, a rotatable cam for controlling the selectiveclosing of the valves, an air pressure system including a control valve for operating the hydraulic actuating means, a rotatable member connected to rotate the cam, a lever for rotating said member, means for axially shifting the rotating member when being rotated to a position causin closing of a shut-off valve, and means operable by the. axial shifting of the rotatable member for Opening the control valve.

14. In a brake actuating system for a vehicle having a driving member for each side thereof, brakes for the members, a-hydraulic actuating means for actuating all the brakes, two shut-off valves each of which is capable of preventing a brake from being actuated, a rotatable cam for controlling the selective closing of the valves, an air pressure system including a control valve for operating the hydraulic actuating means, a rotatable member connected to rotate the cam, a lever for rotating said member, means for axially shiftin the rotating member when being rotated to a position causing closing of a shut-ofi valve, means operable by the axial shifting of the rotatable member for opening the control valve, and means for shifting the rotatable member axially by the lever to open the control valve without rotation of the cam and closing of a shut-off valve. s

15. In a brake actuating system for a vehicle v having a driving member for each side thereof valves each of which is capable of preventing a brake from being actuated, an air pressure sys-- and a dirigible wheel, brakes for the members" and wheel, a hydraulic actuating means for. all the brakes, shut-off valves associated with. the actuating means and each capable of preventing actuation of a brake, an air pressure system including a control valve for operating the hydraulic actuating means, and means including a single member for closing the shut-pit, valve for the brake on the dirigible wheel together with either of the shut-off valves for the brakes of the driving members and for operating the control valve of the air pressure system after the selected shutoff valves are closed.

1 6. In a brake actuating system for a vehicle having a driving member for each side thereof and a dirigible wheel, brakes for the members and wheel, a hydraulic actuating means for all the brakes, shut-oil valves associated with the actuating means and each capable of preventing actuation of a brake, an air pressure system including a control valve for operating the hydraulic actuating means, and means including a single member for closing the shut-off valve for the brake on the dirigible wheel together with either of the shut-off valves for the brakes of the driving members and for operating the control valve of the air pressure system after the selected shut-off valves are closed or for operating the control valve independently without closing any of the shut-off valves.

1'7. In a brake actuating system for a vehicle, a driving member for each side thereof and a dirigible wheel, brakes for the members and wheel, a hydraulic actuating means for all the brakes, shut-off valves associated with. the actuating means and each capable of preventing actuation of a brake, an air pressure system including a control valve for operating the hydraulic actuating means, means including a single manually operable member for closing the shut-oil. valve for the brake on the dirigible wheel together with either" of the shut-off valves for the brakes of the driving members and for subsequently operating the control valve of the air pressure system, means permitting the control valve to be operated by the single member without closing the shut-oi! valves, and means comprising spring means for automatically returning the manually operable member to an inoperative position where the shut-oil valves are open and the control valve is closed whenever the hand of the operator is removed therefrom with the lever in an operative position.

1 8. In a brake actuating system for a vehicle having a driving member for each side thereof, brakes for the members, a hydraulic actuating means for actuating allthe brakes, two shut-oil. valves each capable of preventing a brake from being actuated, a rotatable cam for controlling the selective closing of the valves, said cam having a central position where both shut-oi! valves are open and positions on each side thereof for closing the valves, an air pressure system including a control valve for operating the hydraulic actuating means, a rotatable member connected to rotate the cam, a lever pivoted to the member for rotating said member, means for axially shifting the rotating member when it and the cam are being rotated by the lever in either direction to a cam position causing closing of a shut-ofl valve, means operable by the axial shifting of the rotatable member for opening the control valve, and means establishing a fulcrum for the lever to permit said lever to be so operated as to axially shift the rotatable member and open the control valve only.

19. In abrake actuating system for a vehicle having a driving member for each side thereof and a dirigible wheel, brakes for the members and wheel, a hydraulic actuating means for all the brakes, shut-off valves associated with the actuating means each of which is capable of preventing actuation of a brake, an air pressure system including a control valvefor operating the hydraulic actuating means, and means for closing the shut-01f valve for the brake on the dirigible wheel together with either of the shut-oil valves for the brakes of the driving members and for operating the control valve of the air pressure system after the shut-off valves are closed or for operating the control valve without closing any of the shut-off valves, said last named me ans comprising a manually operable lever movable in one direction from a predetermined position for closing the shut-off valve of the brake on the dirigible wheel, the shut-off valve ofone of the brakes of the driving members and subsequently opening the control valve, movable in another direction from said predetermined position for closing the shut-off valve of the brake on the dirigible wheel, the shut-off valve of the other brake of the driving members and subsequently opening the control valve and movable in a third direction for WERNER F. BOLDT. 

